Abstract

Tetrahedral amorphous carbonfilms were deposited in a filtered cathodic vacuum arc chamber. Nitrogen, of atomic concentration up to was introduced in the films during deposition by a Kaufmann-ion source. Change of the film structure and the valence band (VB) spectra of film due to nitrogen incorporation was studied by ultraviolet photoelectron spectroscopy (UPS) using He I and He II excitations as well as x-ray photoelectron spectroscopy(XPS). A comparative study of the electronic structure between and the nitrogenated films was demonstrated by decomposition of their VB spectra into several bands and from the intensity difference of these spectra. An additional density of states close to the Fermi level representing the nitrogen lone pair state, has been detected from both UPS and XPS VB spectra of nitrogenated samples. From the shift of the VB relative to the nitrogen doping of is demonstrated. The change of the density of states at the edge of VB and especially the and states is thoroughly explained. The modification of the structure of nitrogenated films prepared by applying the substrate bias and temperature was also studied through comparison of the VB spectra.